Known air separation modules (ASMs) are found in aircraft fuel tank flammability reduction systems. The ASM removes some oxygen from air to generate nitrogen-enriched air (NEA), which then flows into fuel tank ullage, a region in the tank that often contains evaporated fuel (i.e., fuel vapor). The NEA may reduce flammability of the fuel tank ullage. Federal Aviation Administration (FAA) regulations require that new and in-service transport aircraft include systems for enhancing the safety of aircraft fuel tanks. Unfortunately, ASMs have a service life that may be limited by reduced separation efficiency or failure of components in the ASM, requiring repair or replacement and causing corresponding aircraft downtime. Accordingly, increased reliability of air separation modules is desirable.